During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. The joint replacement procedure may involve the use of a prosthesis which is implanted into one or more of the patient's bones. In the case of a patella replacement procedure, an orthopaedic prosthesis is implanted into the patient's patella. Specifically, a prosthetic patella implant component is secured to the patient's natural patella such that its posterior surface articulates with a femoral component during extension and flexion of the knee.
Conventional prosthetic patellas may have a dome-shaped polymer bearing or an anatomic or conforming polymer bearing. Anatomic or conforming bearings are designed to conform with the bearing surfaces of the femur. Dome patella components allow for greater movement between the patella component and the femoral component of the knee prosthesis, whereas anatomic patella components are more constrained relative to the femoral component. An example of dome-shaped prosthetic patella is disclosed in U.S. Pat. No. 5,593,450. An example of such an anatomic prosthetic patella is disclosed in U.S. Pat. No. 6,074,425.
To facilitate the replacement of the articulating surface of the natural patella with the prosthetic patella, orthopaedic surgeons use a variety of orthopaedic surgical instruments such as, for example, saws, drills, mills or reamers to resect the posterior surface of the patella and then to prepare the resected surface for fixation of the prosthetic patella.
Common fixation elements for prosthetic patellae include one or more pegs extending out from the bone-facing (anterior) surface to be received in complementary recesses or holes drilled or reamed into the patella. To prepare the patella to receive such a prosthetic patella, the surgeon may resect the posterior portion of the patella to define a flat surface and then uses a drill guide and drill to drill the hole or holes into the resected surface of the patella. However, it is difficult to hold the patella drill guide stationary against the patella while drilling, particularly when the patella is everted: this surgical step may require one hand to hold the patella, another hand to hold the drill guide and a third hand to drill the holes. Also, when cementing the patella implant to the prepared patellar surface, it may be difficult for the surgeon to hold the patella and patella implant in place.